Glass fiber reinforced plastic composites have specific role among thermoset plastics. Thermoset SMC (Sheet Molding Compound) products comprising glass fiber, in particular SMC products based on unsaturated polyester, further BMC (Bulk Molding Compound) products are widely used both outdoor and indoor. According to literature data their large scale use increases exponentially. On the other hand, this increase has significant disadvantages. Like all plastics, they degrade and finally become waste. Their decomposition lasts for many generations, the quick eradication is almost impossible, and the cost-effective recycling is unsolved. When burning a number of harmful substances are released. The reinforcement content further worsens the damaging effect of these composites on health and the environment.
The efforts required to destroy hazardous waste often exceed the efforts necessary to manufacture them. This refers both to technology and the expenses. In extremis, manufacturers may be required to repurchase waste.
Due to its large scale use, disposal of the increasingly accumulating amounts of PET bottle waste represents an increasing problem as well.
One possibility of handling plastic waste is recycling and no wonder that the related literature has considerably developed in the last years. Among the numerous publications dealing with the recyclation of plastic waste, mention can be made of the following cases.
In Hungarian Patent Application P0500050 a process is disclosed wherein thermoplastic granules are mixed with ground glass, for example glass fiber and/or porcelain waste or kaolin, then shaped between heated molding boards on 125 to 130° C. in 15 minutes. During mixing this material is highly abrasive and thus the screw feeder and the cylinder have to be provided with expensive, wear resistant coating. The end-product is an esthetic weather-resistant cover element, an outdoor decor, a flower-box, etc., however it does not show water repellency or water impermeability.
International Publication Document WO96/19336 relates to the preparation of structural elements prepared from thermoplastics containing fibers, and in particular reinforced with glass fiber, like wall-plugs or dowels.
Hungarian Patent Application P0900260 discloses a process for the preparation of sound insulation panel using sintered PET bottle waste. In this process the PET component is sintered on 130 to 160° C. On the effect of heat the PET material, which by itself is amorphous and unbreakable, recrystallizes and becomes brittle and fragile. The main disadvantage of the heat insulation product prepared by this process is that it cannot be prepared in the form of panel, furthermore it is not weldable owing to the properties of the cross-linking material used.
International Publication Document WO01/55524 discloses a multilayer lightweight sandwich panel, wherein the intermediate or core layer is foamed plastic. On each side of this core layer a perforated sheet-metal is placed under the outer layer. This product is continuously prepared by the use of multiple extruders and roll-feeders, and the final shape of the panel is formed between calender rolls.
Hungarian Patent Application P0303065 discloses the preparation of a multilayer plastic insulation sheet or film, wherein one of the layers comprises fiber with random structure, for example glass fiber, on a PVC-based supporting layer, and to one side of this layer another PVC-based layer is attached. Two layers of this product are joined and the final form of the layered sheet is created in continuous process applying line pressure between heated calender rolls. A disadvantage of this product is that its elastic modulus is low, further it cannot be welded.
British Patent Document 2 464 540 relates to a figured composite product comprising an open cell foam layer, a hardened plastic layer and a figured layer, for example a glass veil impregnated with the said hardened layer, where the hardened plastic layer preferably contains a filling agent and a reinforcing fiber and may also contain SMC.
Japanese Patent Document 11 199 684 relates to a layered product containing BMC or SMC sheets usable for decoration purpose, which product gives the impression of transparency.
Japanese Patent Document 11 256 017 relates to a fiber reinforced plastic molding free from unevenness, which can be painted to an even, intense colour.
Hungarian Patent 227033 discloses wear-resistant multilayer elastic sheets usable as covering for general purposes and indoor sports as well. The layer covering the surface of use contains solid particles and a glass fiber framework, and the underlying supporting layer consists of soft PVC, bulk or foamed polymers providing elasticity and flexibility.
None of the above documents disclose the layered products according to the present invention, since the present products are not only filled but also reinforced, contain different types of plastic waste and show excellent properties.
An aim of our work was to provide solution for the safe disposal of the increasingly accumulating amounts of non environmentally friendly thermoset plastic waste. With the present invention we surpassed this aim and created a reinforced layered product which shows advantageous properties, like high tensile strength and flexibility, further excellent heat, sound and electric insulation properties, besides it is easily weldable.